1. Field of the Invention
This invention concerns novel adhesive, molding and binder compositions and more particularly relates to the use of readily available, inexpensive isocyanate waste products in such compositions thus reducing pollution by the waste products and making good adhesive, molding and binder compositions available at low cost.
2. Description of the Prior Art
Diisocyanates, and especially toluene diisocyanates, are important industrial products useful in the manufacture of urethane polymers. They are produced commercially by phosgenation of diamines or mixtures thereof in the presence of a solvent followed by distillation to recover solvent and the diisocyanates or mixtures thereof. Unfortunately, distillation of crude toluene diisocyanates leaves a residue of material from which it is difficult to recover a large portion of the toluene diisocyanate and the material containing the TDI is discarded as a waste product. Toluene diisocyanate is manufactured in large quantities, thus disposal of the large quantities of residue wastes has become a serious problem. As used herein TDI refers to toluene diisocyanate; and "TDI residue" as used herein is the residue remaining after vaporizing toluene diisocyanate from a reaction mixture, which results fom substantially complete phosgenation of toluene diamine, until between about 12 and about 30 percent by weight of toluene diisocyanate remains in the residue. The residue includes from about six to about twenty-five weight percent of unreacted isocyanate groups, and is solid at 25.degree. C.
Prior art processes are known for utilizing the undistilled liquid compositions produced from the manufacture of TDI by the phosgenation of toluene diamine. U.S. Pat. No. 3,341,462 (Shultz et al., 1967) describes the use of a relatively pure liquid composition to which a small amount of a polyol may be added during the production of rigid cellular membranes. U.S. Pat. No. 3,450,653 (McClellan, 1969) describes the use of a polyol in reacting with a polymethylene-polyphenyl-isocyanate mixture to produce polyurethane elastomeric sealants. U.S. Pat. No. 3,755,215 (Khoury et al., 1973) describes the use of a TDI liquid composition for preparing polyurethane foams.
U.S. Pat. No. 3,876,278 (Kuroda et al., 1975) prepares a cured resin by reacting an active hydrogen containing compound with an NCO group-containing distillation residue (TDI residue) obtained in the production of tolylene diamine, in the presence of a polymerizable unsaturated monomer and polymerization catalyst, wherein the resin has adhesive properties. However, the authors state that a satisfactory adhesive resin is not produced by reacting the TDI residue directly with a hydroxyl group-containing compound.